This invention relates to a semiconductor light emitting device, which may be either a semiconductor laser or a semiconductor light emitting diode (LED).
Such semiconductor light emitting devices are widely used in optical communication networks. Semiconductor lasers are generally capable of high speed direct modulation than LED's. Hence, this invention will be described in focus on lasers, although the invention can be applied to both lasers and LED's.
As will be described in detail later, a conventional semiconductor laser comprises an active layer in which free carriers are present to contribute to emission of light through recombination. First and second cladding layers are on both sides of the active layer to confine optical wave and the carriers to the active layer. The first cladding layer has a p-type conductivity. The second cladding layer has an n-type conductivity. First and second electrodes are in ohmic contact with the first and the second cladding layers, respectively.
Various high-speed semiconductor lasers have been already known. Modulation speed is, however, restricted due to a delay involved in the process of emitting light. It is known that the delay includes a life time of carriers as a parameter.